With a trend of miniaturization and multifunctionality of electronic devices, a circuit formed within a semiconductor component needs to be highly densified and operated at a high speed. To this end, in a silicon substrate used as the semiconductor component, for example, multiple layers of circuit boards are stacked on top of each other, and the individual layers are connected by a silicon-through electrode. Copper, which has low electrical resistance and high reliability, is used as the silicon-through electrode.
To form the silicon-through electrode made of copper in the silicon substrate, various kinds of plating processes are performed on a surface of a recess formed in the silicon substrate. First, by electrolessly plating cobalt/tungsten/boron (Co—W—B) on the surface of the recess formed in the silicon substrate, a barrier layer for suppressing diffusion of copper is formed. Then, by electrolessly plating copper on a surface of the barrier layer, a seed layer composed of a single film of the copper is formed. Thereafter, copper is electroplated on a surface of the seed layer made of the copper, so that the copper is buried in the recess formed in the silicon substrate.
Patent Document 1: Japanese Patent Laid-open Publication No. 2010-185113
In the aforementioned conventional plating process, however, it is observed that the barrier layer is peeled off from the silicon substrate when forming the seed layer made of the single film of copper on the surface of the barrier layer. Further, in the aforementioned conventional plating process, it is also observed that the silicon-through electrode (barrier layer, seed layer and buried copper) is peeled off from the surface of the silicon substrate after the silicon-through electrode is formed.
As stated above, if the single film of copper is electrolessly plated on the surface of the film which is formed by the electroless plating, the peeling between the films may occur, so that the reliability of the plating process and the reliability of the component manufactured through the plating process are deteriorated.